Green meteorite may be from Mercury, a first

Scientists may have discovered the first meteorite from Mercury.The
green rock found in Morocco last year may be the first known visitor
from the solar system's innermost planet, according to meteorite
scientist Anthony Irving, who unveiled the new findings this month at
the 44th annual Lunar and Planetary Science Conference in The Woodlands,
Texas. The study suggests that a space rock called NWA 7325 came from
Mercury, and not an asteroid or Mars.

NWA
7325 is actually a group of 35 meteorite samples discovered in 2012 in
Morocco. They are ancient, with Irving and his team dating the rocks to
an age of about 4.56 billion years.

"It
might be a sample from Mercury, or it might be a sample from a body
smaller than Mercury but [which] is like Mercury," Irving said during
his talk. A large impact could have shot NWA 7325 out from Mercury to
Earth, he added. Irving is an Earth and Space Sciences professor at the
University of Washington and has been studying meteorites for years. But
the NWA 7325 meteorite is unlike anything found on Earth before, he
told SPACE.com.

Meteorites
from Mars are imbued with some Martian atmosphere, making them somewhat
simple to tell apart from other rocks. Space rocks from Vesta, one of
the largest asteroids in the solar system, are also chemically distinct,
but NWA 7325 does not resemble any space rock documented by scientists
today.

Irving
thinks that the meteoritewas created and eventually ejected from a
planet or other body that had flowing magma on its surface at some point
in its history. Evidence suggests that the rock could have been formed
as "scum" on the top of the magma, Irving said.

NWA
7325 has a lower magnetic intensity — the magnetism passed from a
cosmic body's magnetic field into a rock — than any other rock yet
found, Irving said. Data sent back from NASA's Messenger spacecraft
currently in orbit around Mercury shows that the planet's low magnetism
closely resembles that found in NWA 7325, Irving said.

Messenger's
observations also provided Irving with further evidence that could
support his hypothesis. Scientists familiar with Mercury's geological
and chemical composition think that the planet's surface is very low in
iron. The meteorite is also low in iron, suggesting that wherever the
rock came from, its parent body resembles Mercury.

While Messenger's first extended mission just finished, the team has
put in a request to continue researching the planet with the orbiter for
the next two years. If the mission is extended until 2015, the science
returned by the spacecraft could help further validate or invalidate
Irving's ideas about the origin of the meteorite.Although finding
meteorites on Earth that came from Mercury is less likely than finding
Martian meteorites, it could be possible, Irving said.